It still bothers me that Kensil put air into a ball and nobody informed the Patriots until Monday morning. From Brady's press conference and all the current and ex-QB's that talked about this issue, one things seemed clear and that is that the QB likes their ball a certain way and they do not want them messed with after they are approved. So for someone to alter the game balls and not inform the Patriots during the freakin' AFCCG is mind blowing and put the Patriots at a disadvantage. Also, what pressure did they fill them to? I wonder if they were at the upper end of the legal spectrum (13.5), especially since it had been reported that Brady likes his balls at 12.5. I mean, if you are gonna mess with the balls you might as well do it "right". I think the Patriots should go on the offensive on this issue, they have a real complaint if these reports are true.
You're 100% correct to bring this up. As a DIRECT RESULT of their re-inflating the balls at half time (for the first time in NFL history),
they forced the Patriots to play the second half with balls that were ILLEGALLY OVER-INFLATED.
I am going to assume that they inflated the balls at half time to the league nominal of 13.0 psig. If this assumption is true, the pressurization of the balls was EQUIVALENT TO balls that had been inflated to 14.3 psi at 75°F.
Well over Brady's preferred 12.5 psig.
Well over the league nominal of 13.0 psig.
And well over the league maximum of 13.5 psig.
[Note: If they reinflated them to TB's choice of 12.5 psig, then they were still "illegally over-inflated", but by a lesser amount: equivalent to 13.8 psig at 75°F.]
How does this happen? Because you can make no statement about a ball's inflation state without knowing the temperature of the air inside the ball.!
Here's the calculation:
The reason that they were overinflated is that most (~93%) of the air inside the football was at about 50F. The pressure inside a Tom Brady's "legally inflated" football (12.5 psig @ 75°F), when the air inside is 50°F MUST BE around 11.2 psi.
We will ignore heating of the introduced air from adiabatic compression in the pump.
The pressure & temperature state of the internal air prior to repressurization was: {11.2 psig @ 50°F}
A very close approximation for the final internal air temp can be estimated by simply “proportioning by pressure" the amount of air in the ball at each temperature.
The final ball pressure will be 13.0 psig = 27.7 psia
The pressure of the air at 50°F = 11.2 psig = 25.7 psia
The percent of air at 50°F in the re-inflated ball will be 25.7 psia/27.7 psia = 93%
The percent of air at 75°F in the re-inflated ball will be 100% - 93% = 7%
The final temp of the re-inflated ball will be very close to .93*(50+460) + 0.07*(75+460) = 511.7°R = 51.7°F.
By our previous calculations, the EQUIVALENT ROOM TEMP PRESSURIZATION of this ball was:
P1 = P2 * (T1/T2) = (13.0+14.7) psia * (75+460)°R / (51.7+460)°R = 29.0 psia = 14.3 psig @ 75°F.
The Pats played with a ball that was EQUIVALENT TO one that had been pressurized & checked in the locker room before the game to an equivalent of 14.3 psig.
And Brady had no trouble throwing this "over inflated" ball. And the receivers had no trouble catching this "over inflated" ball. And the Pats out-scored the Colts 28-0 in the second half.
While they only outscored them 17-7 in the first half, with their "low pressure, but legal" (12.5 psi @ 75°F) footballs.
So much for the "underinflated balls give the passer, receivers & runners an advantage" nonsense.
